Pico Liter Dispensing Using Liquid Bridge Breakup in Immiscible Fluid

Abstract

A simple and robust way is devised to generate picoliter droplets out of a single microliter drop for the use of generating monodisperse droplets in droplet-based microfluidics. A single aqueous drop is placed between two glass substrates and immersed in silicone oil, to form a liquid bridge. Then one substrate is moved with a constant velocity ranging from 50 to 1000 μm/s. As the distance between two glass plates increases, the liquid bridge breaks up and smaller droplets or satellites are formed. It is found that, for the case of fixed outer fluid, the droplets of nearly the same size are generated over several orders of moving velocity. However, the size of a satellite droplet increases as the mother drop size increases, and it decreases as the outer fluid viscosity increases. Based on this result, a picoliter-droplet was successfully dispensed repeatedly for 100 times within 2% relative standard deviation, on-demand. To confirm its feasibility of single particle encapsulation, a single polystyrene microparticle has been captured successfully using this method without complex control.